An amateur fossil-hunter found three more closely related specimens in the 1990s. The additional bones, composing nearly a full skeleton, gave Fordyce and his colleagues a more complete picture of the birds.

But only in more recent years did the researchers realize that they were looking at a significant new group of ancient penguin.

Microfossil dating techniques firmly place the seabirds in the age range of 58 million to 62 million years old, Fordyce says, making them the world's oldest known penguins.

"We are absolutely sure that they come from early Paleocene time, the time that immediately followed the extinction of dinosaurs," which occurred about 65 million years ago, Fordyce said.

Prior to the discovery, the oldest previously described penguin was a fragmentary specimen from Antarctica estimated to be some 55 million years old.

Waimanu pushes the age of early penguins back by millions of years, Fordyce says.

This fact, plus the knowledge that the penguins were highly specialized, suggests the birds descended from other, still-modern species that lived many millions of years further back in time.

"We can use that quite ancient penguin to argue [that] all the other modern [bird] groupsmany of the other modern groups at least[arose] back in Cretaceous times contemporaneous with the dinosaurs," Fordyce said.

Feathered Family Tree

Lacking a clear fossil record, scientists have debated precisely when modern birds first took flight. Some experts believe the group first diversified during the reign of dinosaurs.

Others argue that modern birds appeared only after dinosaurs died out in what proponents of the theory call a "Big Bang" of rapid bird evolution.

While the penguin study may not definitively settle the flap, it does highlight the growing use of genetic detective work by researchers attempting to pinpoint the evolutionary origins of man and beast. (See the Genographic Project.)

Study co-author David Penny, a geneticist with the Allan Wilson Centre for Molecular Ecology and Evolution at Massey University in Palmerston North, analyzed avian DNA sequences to construct a family tree of bird evolution.

Penny and colleagues identified genetic differences between living bird species and the rate at which those DNA changes, or gene mutations, likely occurred over time.

That information enabled his team to use the newly found penguin fossils and a recently described duck relative from the Cretaceous period (145.5 to 65.5 million years ago) found in Antarctica as reference points to establish a time frame for bird evolution.

"From the [DNA] sequences we can build [an evolutionary] tree fairly easily " Penny said. "But that doesn't tell you anything about the times [certain species appeared] until you can get these calibration points from the fossils."

Based his team's work, Penny estimates that modern birds first appeared around 90 million years ago.